Fabrication of optical meta-structure at infrared rang using nanoimprint lithography

Abstract

Negative index meta-material s (NIM) that exhibit unique refractive and focusing properties have recently become a focus of research worldwide. They have opened up new opportunities in nano-photonics and optical integration.1-8The important issue of how to fabricate these meta-structures with high-precision, high-throughput, and low-cost remains a challenge, especially for short wavelengths of radiation (e.g. infrared or even visible range). Here, we report on the development of a fabrication procedure of optical meta-structures using nanoimprint lithography (NIL)9. We will report two types of meta-structures: L-shaped resonators (LSRs), which have a negative permeability at 5 urn range and "fishnet" structure, which is supposed to have both negative permittivity and permeability, hence negative refractive index at around 1.5 μ range. We fabricated the LSRs with smallest feature at 50 nm and better than 10 nm critical dimension (CD) control. (Figure1) LSRs on various substrates, such as Si, Si with Si3N4film and free standing Si3N4 membrane were characterized (Figure 2) and consistent with theoretical predictions. We also studied the metal/dielectric/metal stack fishnet structure10which is more scalable for shorter wavelength. Our theoretical simulation shows that the structure has both negative permittivity and permeability, therefore negative refractive index at 1.5 μm range. (Figure 3) More details in theoretical studies and fabrication issues will be presented too.